.. _build_custom_app:

Build Custom C/C++ App
######################

This guide provides step-by-step instructions for creating a custom C application and building it for the SiMa DevKit using the Yocto Software Development Kit (SDK). It covers developing a simple "Hello World" program, configuring it for cross-compilation, and using the SDK’s tools for building. While similar to standard C/C++ development, this process requires setting up the Yocto cross-compilation environment to target the DevKit’s embedded architecture.

Before you run the following commands, ensure you have :ref:`setup the cross compilation environment <cross_compilation_setup>`.

.. dropdown:: Step 1. Create the Application Source Code
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    First, write a simple C program as your custom application.

    1. Create a project directory and navigate to it:

    .. code-block:: bash

        user@palette-container-id:/home/docker/$mkdir ~/myproject
        user@palette-container-id:/home/docker/$cd ~/myproject

    2. Create a file named ``hello.c`` with the following content:

    .. code-block:: c

        #include <stdio.h>

        int main() {
            printf("Hello, SiMa DevKit!\n");
            return 0;
        }

    This basic program prints a greeting when executed.

.. dropdown:: Step 2. Compile the Application Using the Yocto SDK
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    The Yocto SDK provides a cross-compilation toolchain (e.g., ``aarch64-poky-linux-gcc``). Use it to compile ``hello.c`` for the DevKit’s architecture.

    1. Compile the program:

    .. code-block:: bash

        user@palette-container-id:/home/docker/myproject$ $CC hello.c -o hello

    Here, ``$CC`` expands to ``aarch64-poky-linux-gcc`` with flags like ``--sysroot=/opt/poky/4.0.23/sysroots/cortexa65-poky-linux`` preconfigured by the SDK environment. This generates an executable named ``hello``.

    2. Verify the build:

    .. code-block:: bash

        user@palette-container-id:/home/docker/myproject$ file hello

    Output should resemble:
    ``hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, ...``

.. dropdown:: Step 3. Deploy the Application to the DevKit
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    To run the application, transfer it to the SiMa DevKit and execute it.

    1. Copy the executable to the DevKit (e.g., via ``scp`` if networked):

        .. code-block:: bash

            user@palette-container-id:/home/docker/myproject$ scp hello sima@devkit-ip:~/

        Replace ``user@devkit-ip`` with your DevKit’s SSH credentials and IP address.

    2. Connect to the DevKit via SSH and run the application:

        .. code-block:: bash

            user@palette-container-id:/home/docker/myproject$ssh sima@devkit-ip "./hello"

        Expected output: ``Hello, SiMa DevKit!``